Boiling water: moist heat

Physical Control of Microbial Growth:

1. effects: penetrates better since water is a better conductor of heat than air
2. kills by denaturing proteins
3. not considered a sterilizing agent especially against spores or certain viruses (spores may require 2 hours to destroy)
4. again, organic matter must be removed

Autoclave: pressurized steam of 121ºC for 15-20 min.

Physical Control of Microbial Growth:

1. most dependable method for destruction of all life-forms, including spores
2. disadvantage: cannot be used for some plasticware (those that melt) and dulls instruments
3. useful for blankets, bedding, utensils
4. to check effectiveness, a culture strip containing Bacillus spores is included (later cultured)
5. prevacuum ........: similar method but air is drawn out to decrease processing time

Fractional sterilization

Physical Control of Microbial Growth:

1. employs 30 minutes of steam on three successive days
2. alternate names include intermittent sterilization or tyndalization
3. limited use: some spores fail to germinate or must be in growth media ( cannot guarantee)

Filtration

1. effect is on the DNA of the bacterial cell
2. can reduce airborne contamination effectively
3. can be used to sterilize an environmental surface or hospital room
4. disadvantages: does not penetrate liquids or solids and requires direct contact with object

Isopropyl

Formaldehyde: solid at room temperature

1. Formalin: 37g of solid dissolved in 100ml of water
2. used for embalming & as disinfectant
3. used to weaken viruses to produce vaccines and to produce toxoids
4. acts by inserting an alkyl group into certain regions on nucleic acids & proteins (called an alkylating agent)

Ethylene oxide

1. chemical counterpart of the autoclave for sterilization
2. is useful for disinfecting plastics which melt in the autoclave
3. penetrates well and is a good sporicidal
4. disadvantage: is toxic & explosive: may cause "cold burns'" of the skin

Hydrogen peroxide

1. used on wounds, scrapes, & abrasions
2. six hours exposure in a six percent solution may effect sterilization
3. catalase in tissues encourages its digestion to end products
4. foaming action assists in mechanical removal of microorganisms
5. may inhibit anaerobic bacteria in wounds